The explosive growth of wireless and mobile networks continues proliferation of heterogeneous network devices on the unlicensed spectrum. These devices are often built on distinct PHY layers to serve specific types of applications, and hence cannot directly communicate with one another. For example, WiFi (or IEEE 802.11) and ZigBee (or IEEE 802.15.4) are often deployed in residential environments for mobile Internet access and home-area networking, respectively. Both share the 2.4 GHz ISM band, but adopt different modulation schemes and even different MAC protocols (ZigBee allows for TDMA). Heterogeneity may occur even in the same family of networks. For example, besides the standard 20 MHz bandwidth, WiFi has evolved to have 40 MHz bandwidth in 802.11n and 160 MHz bandwidth in 802.11ac to support high date-rate applications, in addition to the 802.11-2007 with narrower bandwidths (5 MHz and 10 MHz) supporting applications with low data-rate but high energy-efficiency. This trend towards heterogeneous MAC/PHY layers is likely to continue with the evolution of wireless networks.
Ideally, each network should independently manage its associated devices. Interference between different networks can be avoided with CSMA-style MAC protocols. However, network heterogeneity poses significant challenges on existing protocols. High-speed devices may preempt low-speed devices and cause severe collision even with CSMA enabled. Hidden terminals worsen the problem, since heterogeneous transmitters cannot exchange the RTS/CTS style signaling messages between them. Lack of a coordination mechanism also renders it infeasible to realize protocols that put the receiver in a narrower spectrum (i.e., lower sampling-rate) than the transmitter in order to save energy.
A straightforward way to enable coordination between heterogeneous network devices is to enforce a common modulation scheme and message format. However, this requires substantial modification to the PHY layers and loses the unique advantages of each device. For example, to enable ZigBee to decode a WiFi-modulated packet, it needs to increase the spectrum width and clock-rate, thus increasing the energy cost. On the other hand, WiFi loses its throughput advantage if it chooses to coordinate using a ZigBee-compatible PHY layer. Therefore, it is essential to develop a lightweight mechanism that does not require modification of the hardware and communication algorithms in existing devices.
This section provides background information related to the present disclosure which is not necessarily prior art.